Don't swallow MODULE_NOT_FOUND error (#24577)

## Bug

- [x] Related issues linked using [`fixes #24328`](https://github.com/vercel/next.js/pull/24328#issuecomment-828847472)
- [ ] Integration tests added

The change in #24328 will swallow any `MODULE_NOT_FOUND` errors triggered in the page. If you for example have a page with a broken import, it will tell you `Error: Failed to load /whatever`. This of course doesn't really tell people what is going on internally (a broken import). I added a check to see if the error actually happened in the page.

packages/next/next-server/server/load-components.ts

@@ -74,20 +74,9 @@ export async function loadComponents(
     } as LoadComponentsReturnType
   }
 
-  let DocumentMod
-  let AppMod
-  let ComponentMod
-
-  try {
-    DocumentMod = await requirePage('/_document', distDir, serverless)
-    AppMod = await requirePage('/_app', distDir, serverless)
-    ComponentMod = await requirePage(pathname, distDir, serverless)
-  } catch (err) {
-    if (err.code === 'MODULE_NOT_FOUND') {
-      throw new Error(`Failed to load ${pathname}`)
-    }
-    throw err
-  }
+  const DocumentMod = await requirePage('/_document', distDir, serverless)
+  const AppMod = await requirePage('/_app', distDir, serverless)
+  const ComponentMod = await requirePage(pathname, distDir, serverless)
 
   const [
     buildManifest,